PASSWD(1)                         User Commands                        PASSWD(1)

       passwd - change user password

       passwd [options] [LOGIN]

       The passwd command changes passwords for user accounts. A normal user may
       only change the password for their own account, while the superuser may
       change the password for any account.  passwd also changes the account or
       associated password validity period.

   Password Changes
       The user is first prompted for their old password, if one is present.
       This password is then encrypted and compared against the stored password.
       The user has only one chance to enter the correct password. The superuser
       is permitted to bypass this step so that forgotten passwords may be

       After the password has been entered, password aging information is
       checked to see if the user is permitted to change the password at this
       time. If not, passwd refuses to change the password and exits.

       The user is then prompted twice for a replacement password. The second
       entry is compared against the first and both are required to match in
       order for the password to be changed.

       Then, the password is tested for complexity. As a general guideline,
       passwords should consist of 6 to 8 characters including one or more
       characters from each of the following sets:

       •   lower case alphabetics

       •   digits 0 thru 9

       •   punctuation marks

       Care must be taken not to include the system default erase or kill
       characters.  passwd will reject any password which is not suitably

   Hints for user passwords
       The security of a password depends upon the strength of the encryption
       algorithm and the size of the key space. The legacy UNIX System
       encryption method is based on the NBS DES algorithm. More recent methods
       are now recommended (see ENCRYPT_METHOD). The size of the key space
       depends upon the randomness of the password which is selected.

       Compromises in password security normally result from careless password
       selection or handling. For this reason, you should not select a password
       which appears in a dictionary or which must be written down. The password
       should also not be a proper name, your license number, birth date, or
       street address. Any of these may be used as guesses to violate system

       You can find advice on how to choose a strong password on

       The options which apply to the passwd command are:

       -a, --all
           This option can be used only with -S and causes show status for all

       -d, --delete
           Delete a user's password (make it empty). This is a quick way to
           disable a password for an account. It will set the named account

       -e, --expire
           Immediately expire an account's password. This in effect can force a
           user to change their password at the user's next login.

       -h, --help
           Display help message and exit.

       -i, --inactive INACTIVE
           This option is used to disable an account after the password has been
           expired for a number of days. After a user account has had an expired
           password for INACTIVE days, the user may no longer sign on to the

       -k, --keep-tokens
           Indicate password change should be performed only for expired
           authentication tokens (passwords). The user wishes to keep their
           non-expired tokens as before.

       -l, --lock
           Lock the password of the named account. This option disables a
           password by changing it to a value which matches no possible
           encrypted value (it adds a ´!´ at the beginning of the password).

           Note that this does not disable the account. The user may still be
           able to login using another authentication token (e.g. an SSH key).
           To disable the account, administrators should use usermod
           --expiredate 1 (this set the account's expire date to Jan 2, 1970).

           Users with a locked password are not allowed to change their

       -n, --mindays MIN_DAYS
           Set the minimum number of days between password changes to MIN_DAYS.
           A value of zero for this field indicates that the user may change
           their password at any time.

       -q, --quiet
           Quiet mode.

       -r, --repository REPOSITORY
           change password in REPOSITORY repository

       -R, --root CHROOT_DIR
           Apply changes in the CHROOT_DIR directory and use the configuration
           files from the CHROOT_DIR directory.

       -S, --status
           Display account status information. The status information consists
           of 7 fields. The first field is the user's login name. The second
           field indicates if the user account has a locked password (L), has no
           password (NP), or has a usable password (P). The third field gives
           the date of the last password change. The next four fields are the
           minimum age, maximum age, warning period, and inactivity period for
           the password. These ages are expressed in days.

       -u, --unlock
           Unlock the password of the named account. This option re-enables a
           password by changing the password back to its previous value (to the
           value before using the -l option).

       -w, --warndays WARN_DAYS
           Set the number of days of warning before a password change is
           required. The WARN_DAYS option is the number of days prior to the
           password expiring that a user will be warned that their password is
           about to expire.

       -x, --maxdays MAX_DAYS
           Set the maximum number of days a password remains valid. After
           MAX_DAYS, the password is required to be changed.

           Passing the number -1 as MAX_DAYS will remove checking a password's

       Password complexity checking may vary from site to site. The user is
       urged to select a password as complex as he or she feels comfortable

       Users may not be able to change their password on a system if NIS is
       enabled and they are not logged into the NIS server.

       The following configuration variables in /etc/login.defs change the
       behavior of this tool:

       ENCRYPT_METHOD (string)
           This defines the system default encryption algorithm for encrypting
           passwords (if no algorithm are specified on the command line).

           It can take one of these values: DES (default), MD5, SHA256, SHA512.

           Note: this parameter overrides the MD5_CRYPT_ENAB variable.

       MD5_CRYPT_ENAB (boolean)
           Indicate if passwords must be encrypted using the MD5-based
           algorithm. If set to yes, new passwords will be encrypted using the
           MD5-based algorithm compatible with the one used by recent releases
           of FreeBSD. It supports passwords of unlimited length and longer salt
           strings. Set to no if you need to copy encrypted passwords to other
           systems which don't understand the new algorithm. Default is no.

           This variable is superseded by the ENCRYPT_METHOD variable or by any
           command line option used to configure the encryption algorithm.

           This variable is deprecated. You should use ENCRYPT_METHOD.

       OBSCURE_CHECKS_ENAB (boolean)
           Enable additional checks upon password changes.

       PASS_ALWAYS_WARN (boolean)
           Warn about weak passwords (but still allow them) if you are root.

       PASS_CHANGE_TRIES (number)
           Maximum number of attempts to change password if rejected (too easy).

       PASS_MAX_LEN (number), PASS_MIN_LEN (number)
           Number of significant characters in the password for crypt().
           PASS_MAX_LEN is 8 by default. Don't change unless your crypt() is
           better. This is ignored if MD5_CRYPT_ENAB set to yes.

           When ENCRYPT_METHOD is set to SHA256 or SHA512, this defines the
           number of SHA rounds used by the encryption algorithm by default
           (when the number of rounds is not specified on the command line).

           With a lot of rounds, it is more difficult to brute forcing the
           password. But note also that more CPU resources will be needed to
           authenticate users.

           If not specified, the libc will choose the default number of rounds

           The values must be inside the 1000-999,999,999 range.

           If only one of the SHA_CRYPT_MIN_ROUNDS or SHA_CRYPT_MAX_ROUNDS
           values is set, then this value will be used.

           If SHA_CRYPT_MIN_ROUNDS > SHA_CRYPT_MAX_ROUNDS, the highest value
           will be used.

           User account information.

           Secure user account information.

           Shadow password suite configuration.

       The passwd command exits with the following values:


           permission denied

           invalid combination of options

           unexpected failure, nothing done

           unexpected failure, passwd file missing

           passwd file busy, try again

           invalid argument to option

       chpasswd(8), passwd(5), shadow(5), login.defs(5), usermod(8).

shadow-utils 4.8.1                 01/23/2020                          PASSWD(1)